1. Field of the Invention
This invention relates to a reader apparatus which converts information of an original surface or a surface to be examined into an electrical signal and reads the same. The apparatus of the present invention is usable with an image information processing apparatus such as facsimile, laser beam printer, ink jet printer or the like and may also be utilized with an apparatus for inspecting the flaw or flaws on the surface of an object. In this specification, the surface including the surface to be examined such as the surface whose flaw is to be inspected is referred to the original surface.
2. Description of the Prior Art
There are various methods of optically reading the information on an original surface, and for example, one of them is the method using a flying spot, but the method to which the present invention pertains comprises illuminating a line on an original surface 1, as shown in FIG. 1 of the accompanying drawings, converting the dispersion light 4 therefrom into an electrical signal by a photoelectric sensor 5 and moving the illuminated line relative to the original surface to thereby two-dimensionally read the information on the original surface. A most basic apparatus of this type is disclosed in U.S. Pat. No. 3,489,909. With this apparatus, the illumination of the line is effected by the use of a cylindrical lens and the information on the illuminated line is integrated to obtain an information signal for inspecting the flaw. In contrast, there is an apparatus as shown in U.S. Pat. No. 3,588,513 which uses a head comprising a plurality of photoelectric transducers arranged in the direction of the line to enhance the resolution in the direction of the illuminated line. However, according to the prior art, it has been impossible to make a photoelectric transducer having a resolution below 1 mm for the usual original width of 20 to 40 cm while, on the other hand, a solid photographing element of high resolving power such as one-dimensional charge coupled device (CCD) could only be several centimeters in length and therefore, in order to read the information on the original surface at a high resolving power, a reduced image of the illuminated line on the original surface had to be formed on the solid photographing element by the use of a reducing optical system and then photoelectrically converted.
However, the apparatus for forming a reduced image of the illuminated line on a solid photographing element of high resolving power by the use of a reducing optical system and photoelectrically converting the same has required a long conjugate distance for image formation between the original surface and the solid photographing element which has in turn led to the larger size of the apparatus and moreover, the finite opening of the reducing optical system has resulted in a decreased quantity of the image plane light on the solid photographing element surface, which has also led to a reduced sensitivity, and, in addition, the quantity of the image plane light has been decreased as it departs from the optic axis, thus making it impossible to maintain a uniform sensitivity.
However, due to the recent advancement of the technique, photoelectric sensors have been developed which are of high resolving power, namely, which enable sensor elements which are the minimum unit capable of separating and reading information light to be minute and which enables a very long footage to be achieved. It has thus become possible to realize a novel form of apparatus which uses such photoelectric sensors instead of the reducing optical system to read information on the original surface.